Expandable implant with expander

ABSTRACT

An at least in part cylindrical threaded interbody spinal fusion implant having an expandable height.

The present application is a continuation of application Ser. No.10/335,286, filed Dec. 31, 2002; which is a divisional of applicationSer. No. 09/551,964, filed Apr. 19, 2000, now U.S. Pat. No. 6,500,205;all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an improved interbody (forplacement at least in part between adjacent vertebral bodies) threadedspinal fusion implant only for the immobilization of vertebrae and notto non-threaded implants. In particular, the invention relates to athreaded spinal fusion implant that is selectively directionallyexpandable and which specifically has height raising capabilities thatare utilized once the implant is initially positioned. Moreparticularly, the invention relates to a threaded implant having arcuateportions of upper and lower members that in a first, collapsed, orinsertion position are parallel to one another and form at least aportion of a cylinder along a substantial portion of the length of theimplant.

2. Description of the Related Art

Threaded spinal fusion implants are known in the related art. The firstartificial threaded spinal fusion implant was invented by Michelson andis disclosed in U.S. Pat. No. 5,015,247, which is hereby incorporated byreference.

Lordotic, frusto-conical, or tapered, threaded spinal fusion implantsare also known in the art. By way of example, Michelson has inventedsuch implants as disclosed in U.S. application Ser. No. 08/480,904,which is hereby incorporated by reference.

Expandable fusion implants are known in the related art. The firstexpandable spinal fusion (allowing for the growth of bone from vertebralbody to vertebral body through the implant) implant was invented byMichelson and is disclosed in U.S. Pat. No. 5,776,199, which is herebyincorporated by reference.

Lordotic, frusto-conical, or tapered, spinal fusion implants have theadvantage of restoring or enhancing spinal lordosis. Threaded spinalfusion implants offer the advantage of being easily positioned in theimplantation space and of having excellent fastening or holdingfeatures. Expandable fusion implants offer the advantage of allowing forthe placement of a potentially larger implant through a smaller openingin a patient's body. Selective expansion along a single direction, (e.g.vertically only when correctly installed) offers the advantage ofincreasing the height of the implant and therefore the distraction ofthe disc space, but without a concomitant increase in the width of theimplant.

There exists a need for an artificial interbody spinal fusion implantproviding for all of the aforementioned advantages in combination.

SUMMARY OF THE INVENTION

In accordance with the present invention, as embodied and broadlydescribed herein, there is provided an expandable threaded artificialinterbody spinal fusion implant, generally cylindrical when inserted,for insertion across a disc space between two adjacent vertebral bodiesof a human spine. The threaded implant of the present invention includesan upper member having an arcuate portion adapted for placement towardand at least in part within one of the adjacent vertebral bodies and alower member having an arcuate portion adapted for placement toward andat least in part within the other of the adjacent vertebral bodies. Thearcuate portions of the upper and lower members have at least oneopening in communication with one another for permitting for the growthof bone from a vertebral body to an adjacent vertebral body through theimplant. The upper and lower members are articulated therebetween,preferably proximate one of the proximal ends and the distal ends of theupper and lower members and preferably allow for divergence between thearticulating members at the end opposite the articulating end of theimplant. The upper and lower members have a first position relative toone another that allows for a collapsed implant height and a secondposition relative to one another that allows for an increased height.The arcuate portions of the upper and lower members in the firstposition of the present invention are parallel to one another and format least a portion of a cylinder along the length of the implant. Aportion of at least one helical thread is on the exterior of each of theopposed arcuate portions of the upper and lower members for engaging theadjacent vertebral bodies. The upper and lower members have a leading ordistal end, an opposite trailing or proximal end, and a lengththerebetween. A blocker that is preferably in the form of an expander islocated proximate at least one of the ends for holding at least aportion of the upper and lower members apart so as to maintain theincreased height of the implant and resist the collapse of the implantto the collapsed implant height. Expansion of the implant preferablyincreases the implant height only, that is in a plane passing throughthe mid-longitudinal axis of the implant and the upper and lowermembers.

The blocker need not be in contact with the upper and lower members whenthe implant is initially inserted into the implantation space. Theblocker may be a block or any type of spacer that is inserted between orotherwise holds apart the articulated upper and lower members after theimplant is positioned so as to hold portions of the upper and lowermembers spaced apart the optimal height and angulation relative to oneanother. That is the implant may be expanded with an extrinsic tool andthen the expanded portions held apart in the second position by a thirdbody blocker or blockers placed therebetween. Further, a physician maybe able to select from a series of blockers having different heightsusable with the same implant. The present invention includes expandingthe implant with a tool, such as a spreader or a distractor, but is notlimited to a scissors type, a rack and gear type, a threaded member typeor any other type of particular external expander tool mechanism. Eachtool nevertheless preferably engages the upper and the lower implantmembers to urge the implant apart. Then the blocker may be inserted intocontact with the upper and lower members to maintain the implant at anexpanded height. The height of the gap created by expanding the implantmay be measured so that the appropriately sized blocker or expander maybe inserted into contact with the upper and lower members depending uponthe amount of distraction of the implant desired by the physician.

In a preferred embodiment, the blocker is in contact with the upper andlower members prior to the implant expansion, and the blocker is itselfthe expander, which may be operated by an extrinsic tool. By way ofexample only, the expander may rotate: to increase the height of theimplant; in a single direction; more than 40 degrees and less than 140degrees and more preferably approximately 90 degrees to move from afirst insertion position to a second/deployed position; and in a planeperpendicular to the longitudinal axis of the implant to increase theheight of the implant. The expander preferably remains in the sameperpendicular plane relative to the longitudinal axis of the implantwhen rotated. In another embodiment the expander may be a member, suchas a plate, a rod, or of any other configuration suitable for theintended purpose initially within the interior between the upper andlower members in a collapsed position that is erected to a more erectposition when the implant is in the expanded position. The expander canitself be hollow or solid.

In a preferred embodiment, the expander preferably has means including,but not limited to, an opening, a projection, or a detent adapted tocooperatively engage a tool used to rotate the expander to increase theheight of the implant. The opening, projection, or detent is adapted tocooperatively engage a tool that preferably rotates about an axisparallel to the longitudinal axis the implant to rotate the expander toincrease the height of the implant. Rather then having an opening, aprojection, a detent, or a central aperture, the expander may have twoor more recesses or holes placed on or through the proximal face toengage a tool. In an alternative embodiment of the expander, cutouts maybe positioned along a portion of the perimeter of the expander.

The expander is preferably located proximate at least one of theproximal end or the distal end of the upper and lower members. Theexpander, however, need not be so located. The expander may be spacedaway from the end and even permit a hollow portion to exist on both theproximate and distal sides of the expander. The upper and lower memberspreferably have an interior surface therebetween and a hollow definedtherein with the expander located proximate one of the longitudinal endsof that interior hollow. The hollow between the ends of the upper andlower members is preferably unobstructed by the expander so as to permitgrowth of bone directly through the hollow unobstructed by the expanderfrom vertebral body to vertebral body through the implant transverse tothe longitudinal axis. The implant may comprise a second and lesserhollow extending at least in part from said expander to the end of theupper and lower members proximate that expander. A preferred expandermechanism includes an expander in combination with cooperating surfacesof the end wall of the implant that guide and support the expander.

Preferred forms of interbody spinal fusion implants have a substantialhollow portion. Certain expandable interbody spinal fusion implants thatincrease in height only of the related art contain an expansionmechanism passing longitudinally therethrough or an expansion mechanismthat is configured for movement of the expansion mechanism fromproximate one end of the hollow portion to proximate the other end ofthe hollow portion, thus requiring the expander to pass through thelength of the hollow portion. A preferred embodiment of the presentinvention overcomes these limitations.

The expander moves the arcuate portions of the upper and lower membersfrom a parallel orientation to an angled orientation relative to oneanother or from a first height at each end to a second and greaterheight at at least one and possibly both ends, but in either event thearcuate portions of the upper and lower members in the first orinsertion position are parallel to one another over a substantialportion of the length of the implant, and/or form at least a portion ofa cylinder along the length of the implant. Each of the upper and lowermembers may structurally cooperate with a blocker, or expander so as tokeep it located so as to function for its intended purpose. By way ofexample, each of the upper and lower members preferably has a trackwithin which the blocker may be captured or the expander rotated. Thetracks may be configured to permit the expander to rotate therein andthen to move from side to side therewithin. The track of the uppermember and the track of the lower member are preferably in the sameplane and the plane is preferably perpendicular to the longitudinal axisof the implant.

A preferred expander has a first height in a first or insertion positionand a greater second height when rotated or positioned into a second ordeployed position to increase the maximum height of the implant from afirst maximum height to a second maximum height. By way of example, atleast one of the tracks of the upper and lower members preferably has acooperating surface and the expander has a corresponding cooperatingsurface that contacts the cooperating surface of the track to orient theexpander in a predetermined position. The cooperating surfacespreferably orient the expander within the implant such that the axis ofrotation of the expander is parallel with the longitudinal axis of theimplant and, more preferably, center the expander within the implantsuch that the axis of rotation of the expander coincides with thelongitudinal axis of the implant. As may be advantageous for the furtherloading of the implant with fusion-promoting material, the expander maycooperate with the tracking surfaces of the upper and lower members toallow the expander to slide from side-to-side for easier access to theimplant interior.

The implant is preferably packed full of bone or other fusion-promotingsubstances prior to expansion of the implant. Expansion of the implantresults in a space being formed in the implant interior into whichadditional fusion promoting substances such as bone may preferably bepacked. Rotating the expander within the implant causes a void that canbe filled with bone. If the expander is configured to permitside-to-side movement, then packing of additional bone into the implantis easy.

When installing a preferred implant from the posterior approach to thespine, the implant is driven from the trailing end and the expander isat the leading end at the anterior aspect of the spine. When expanded,the implant installed from the posterior aspect leaves a void at theleading end of the implant near the anterior aspect of the spine becausethe leading end of the implant has been made taller. Additionally, thepath left behind in the bone filled interior of the implant by the toolused to access the expander through the bone filled interior to positionthe expander is preferably packed with bone as well.

In a preferred embodiment of the present invention, the expander heightchange from the first position to the second position corresponds tosubstantially the same change in height of the implant along at least aportion of the length of the implant. The expander may be configured indifferent ways. A preferred configuration for a rotational expanderincludes: a first dimension corresponding to the width of the expanderwhen the implant is initially inserted into the spine and to the heightof the rotational expander when the rotational expander is rotated toincrease the height of the implant; and a second dimension correspondingto the height of the expander when the implant is initially insertedinto the spine and to the width of the expander when the expander isrotated to increase the height of the implant. The first dimensionpreferably is greater than the second dimension.

The expander may have an upper surface, a lower surface, and sidesurfaces as defined when the expander is positioned after rotation toincrease the height of the implant. As used herein, the term “sidesurfaces” refers to those portions of the expander that extend from theupper member to the lower member after the expander has been rotatedinto its second or deployed position to increase the height of theimplant. The “upper” and “lower” expander surfaces refer to thoseportions of the expander that are in contact with the upper and lowermembers when the implant is in its second or expanded configuration.Each of the upper and lower surfaces of the expander may lie generallyin a plane and may be generally parallel to one another. The sidesurfaces and the upper and lower surfaces may be oriented so as tosubstantially form a parallelogram, which will typically be in the shapeof a rectangle generally.

A preferred expander is in the form of a modified rectangle or rhomboid.The expander generally has a longer dimension and a shorter dimension.When the expander is in a first position, the short dimension spans thedistance between the upper and lower members and when the expander is inthe second position, the expander's long dimension spans the distancebetween the upper and lower members.

The expander may have a cross-section with the side surfacesintersecting the upper and the lower surfaces at junctions, which may betwo diametrically opposed corners and two diametrically opposed arcs.The two diametrically opposed arcs may be each of the same radius and,preferably, the diagonal or modified hypotenuse “MH” between the opposedarcs has a maximum dimension that generally approximates the distancebetween the upper and lower surfaces such that, when the expander isrotated from a first insertion position toward a second/deployedposition, no substantial over-distraction occurs between the adjacentvertebral bodies as would occur if the height of the implant wasincreased markedly beyond that obtained in the second/deployed position.The two diametrically opposed corners may form a 90-degree angle. Theexpander preferably has a fixed shape during movement from a firstinsertion position to a second/deployed position within the implant.

In a preferred embodiment, a modified hypotenuse or diagonal “MH” is thedimension between the two diametrically opposed arcs that allows for therotation of the expander from a first position to a second positionwithout substantial over-distraction occurring during this process. Thephrase “without substantial over-distraction” is defined as distractingthe vertebral bodies in the range of elastic deformation and short ofplastic deformation and tissue failure. To avoid any ambiguity regardingthe phrase “without over-distraction,” this phrase and the individualwords contained therein are not being used as they may be in theirnormal or ordinary use, but are being used as defined in thisapplication only. In the example of this rotational expander, the MHcould be identical in length to the height thereby assuring literally nooverdistraction. It may be preferred, however, to have the MH justslightly greater in length than the height to insure the stability ofthe expander in the expanded or second position because this would thenrequire additional force over the stable position to derotate theexpander.

In accordance with an embodiment of the present invention, a secondexpander may be located between the upper and lower members for movingat least a portion of the upper and lower members away from one anotherto increase the height of the implant as defined by the maximum distancebetween the arcuate portions of the upper and lower members proximatethat expander. All of the features described herein for the expander mayalso be applicable to the second expander. Additionally, the secondexpander may be located proximate an end of the implant opposite theother expander, thereby providing an implant capable of being expandedat both ends of the implant. The increased height of the implantresulting from moving the two expanders may be constant or varied alongthe length of the implant according to the desired configuration of theimplant and the relative dimensions of the individual expanders. A givenimplant may be adapted to receive or cooperatively engage a series ofprogressively sized (taller) blockers or expanders to allow the surgeonto make a final height selection at the time of surgery.

In accordance with an embodiment of the present invention, the implantmay include an expansion mechanism including the expander and at leastone partial wall structure preferably located proximate an implant endthat guides and holds the expander in a predetermined position.

The implant may have an overlapping step-cut wall junction between theupper and lower members, which offers as some of its advantages:increasing the lateral rigidity of the implant, holding the implant inthe closed first position until expanded, and to the extent desiredretaining the fusion-promoting materials within the implant. The walljunction may be either solid or perforated.

One of the upper and lower members preferably has an interior wallextending toward the other of the upper and lower members and, morepreferably, has two interior walls extending from each side of thearcuate portion. The interior walls may be aligned parallel with thelongitudinal axis of the implant. The other one of the upper and lowermembers preferably has an interior-contacting surface adapted to contactor receive the interior longitudinal wall.

By way of example, one of the upper and lower members may have alongitudinally extending interior wall, which is preferably unexposed,extending toward the other of the upper and lower members when theimplant is in an initial insertion position. When the implant is in thefinal expanded or deployed position the implant has a preferred shapesuch that each of the arcuate portions of the upper and lower membersare separated by at least a portion of interior wall, which in thisposition preferably has an exposed side.

The upper and lower members in certain embodiments are articulated toone another so one of the respective ends of the upper and lower membersremain articulated while the other of the respective ends of the upperand lower members are free to move away from one another. In a preferredembodiment, the articulating means is achieved without a third member,such as an axle shaft, for example, passing through the implant. Thearticulating means preferably is formed into the implant wallsthemselves, and in a further preference in such a way that thetwo-implant halves may be articulated when at 90 degrees to each other.The halves then are moved, much like a book closing, toward each otherprior to insertion into the implantation space in the spine. Once theupper and lower members are closed from the approximately 90 degreesarticulating position, much like closing the leaves of a book, the upperand lower members of the implant are locked together at the articulationso that the members will not disarticulate when in use. Other types ofarticulation as would be known to one of ordinary skill in the art arewithin the scope of the present invention.

By way of example, the upper and lower members preferably have acooperating rotational articulation or pivot point between a proximateone of the proximal end and the distal end of the upper and lowermembers. The cooperating rotational articulation preferably is proximateone of the proximal end and the distal end of the upper and lowermembers at an end opposite the expander when only one end is to beexpanded. A preferred rotational articulation configuration includescooperating brackets and projections configured such that articulationtherebetween occurs when the upper and lower members are substantiallyperpendicular to one another. Such a configuration offers the advantagethat the brackets and the projections will not disengage one anotherwhen articulated for use such as insertion into the spine and subsequentexpansion within a range of movement of the upper and lower membersresulting from the expander positioning.

When the implant is in the final or expanded position the implant maytake the general form of a cylinder split along a horizontal planethrough its mid-longitudinal axis wedged upper half from lower half byan inclined plane.

At least one and preferably both of the upper and lower members may havea screw hole passing through the trailing end, which preferably isadapted to receive a screw passing through the end of the upper andlower members and from the interior of the implant into each of theadjacent vertebral bodies to anchor the implant, further stabilize thosevertebral bodies relative to each other, prevent undesirable motion atthe vertebral body implant interfaces, increase the compressive load atthe implant trailing end, prevent rocking and thereby to mitigateagainst excessive peak loads, and to more uniformly distribute loadsimparted to the implant over the length of the implant to the adjacentvertebral bodies. The implant may have a side configured, when in theexpanded position, to cooperate with another interbody spinal fusionimplant so as to allow the pair of implants to have a reduced combinedwidth.

The trailing end of the implant preferably has a tool-engaging portion,but the implant may be adapted to cooperatively engage a driver atanother location or by any means as would be known to one of ordinaryskill in the art. This tool-engaging portion is adapted to engage aninsertion tool that holds and rotates the implant into position. Theconfiguration of the tool-engaging portion may be an opening, and moreparticularly an opening that is along the longitudinal axis of theimplant to facilitate the use of an insertion tool that rotates theimplant into an inserted position. It is appreciated that thetool-engaging portion need not be an opening. A hole or a blind hole,threaded or otherwise, is preferred in another embodiment. In anotherpreferred embodiment the opening preferably is a threaded slot thatfunctions to cooperatively engage and disengage a tool for use ininserting the implant. In specific embodiments, the leading or trailingend may have wall portions, and/or be adapted to cooperatively engage acap. Either the end wall portions or a cap may have an opening oropenings which may function to hold fusion-promoting materials withinthe implant and/or, permit vascular access and bone growth therethrough.

For an embodiment of an implant of the present invention having oneexpander, the main access opening is preferably at the end opposite fromthe expander. The main opening may be at either the distal or proximalend of the implant. The end of the upper and lower members containingthe expander may serve as a secondary access opening.

By way of example, an implant configured for insertion from an anteriorapproach may be initially packed from the distal or leading end of theimplant. The implant is then driven into position. Once the expander ismoved into final position and any associated tool for positioning theexpander is withdrawn from the expander, any void in the bone packedinto the implant interior may be filled. The expander may be moved fromside-to-side to pack more bone into the implant. In essence, theside-to-side movement of the expander provides for a secondary accessopening for accessing the hollow interior of the implant and forcompressively loading it with fusion-promoting substances. Theaccompanying drawings, which are incorporated in and constitute a partof this specification, are by way of example only and not limitation,and illustrate several embodiments of the invention, which together withthe description, serve to explain the principles of the invention. Thescope of the invention is limited only by the scope of the claims asfrom the present teachings other embodiments of the present inventionshall be apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a spinal fusion implant of oneembodiment of the present invention;

FIG. 1A is a perspective view of an alternative embodiment of a blockerin the form of an expander for use with the spinal fusion implant ofFIG. 1;

FIG. 1B is a perspective view of another alternative embodiment of ablocker for use with the spinal fusion implant of FIG. 1;

FIG. 1C is a perspective view of yet another alternative embodiment of ablocker for use with the spinal fusion implant of FIG. 1;

FIG. 2 is a top plan view of the implant of FIG. 1;

FIG. 3 is a trailing end view of the implant of FIG. 1;

FIG. 4 is a side elevation view of the implant of FIG. 1;

FIG. 5 is a leading end view of the implant with the end cap thereattached of FIG. 1;

FIG. 6 is a cross-sectional view along line 6-6 of FIG. 2;

FIG. 7 is a cross-sectional view along line 7-7 of FIG. 5;

FIG. 8 is a side elevation view of an end cap for use with the implantof FIG. 1;

FIG. 9 is a schematic representation of a geometric configuration of across-section of an expander in accordance with one embodiment of thepresent invention;

FIG. 10 is a trailing end perspective view of the implant of FIG. 1;

FIG. 11 is a side view of the implant of FIG. 10 being inserted from agenerally anterior approach to the spine into an implantation siteformed across a disc space and two adjacent vertebral bodies of thespine shown in partial cross-section;

FIG. 12A is a cross-sectional view of the implant of FIG. 1 inserted inan implantation site formed across the disc space and two adjacentvertebral bodies of the spine;

FIG. 12B is a cross-sectional view of the implant of FIG. 1 inserted inan implantation site of FIG. 12A and expanded to place the adjacentvertebral bodies in proper lordosis;

FIG. 12C is a trailing end perspective view of the implant of FIG. 1with the implant in an expanded position;

FIG. 13 is a trailing end view of the anterior aspect of two adjacentvertebral bodies and two implants of FIG. 1 implanted therebetween in afinal position;

FIG. 14 is a cross-sectional side view of an implantation site formedposteriorly across the disc space between two adjacent vertebral bodiesand a second embodiment of an implant of the present invention forposterior insertion being installed into the implantation site;

FIG. 15 is a cross-sectional side view of the implantation site formedacross the space between two adjacent vertebral bodies and the implantof FIG. 14 installed into the implantation space;

FIG. 16 is a leading end perspective view of the implant of FIG. 14;

FIG. 17 is a top plan view of another embodiment of the presentinvention inserted upon the lower vertebral body of an implantation siteformed anteriorly across a disc space with the vertebral body shown inpartial cross-section;

FIG. 18A is a cross-sectional side view of the implantation site formedacross the space between two adjacent vertebral bodies and one of theimplants of FIG. 17 installed into the implantation space;

FIG. 18B is a trailing end view of the anterior aspect of two adjacentvertebral bodies and the implant of FIG. 17 implanted therebetween in anexpanded position as well as another embodiment designed to be used as aside-by-side pair;

FIG. 19 is a cross-sectional side view of the implant of FIG. 18Awithout bone or other fusion-promoting substances shown therein for thepurpose of illustrating a preferred configuration for articulating theupper and lower members together with a hook and peg configuration thatprevents the implant from over expanding and with an alternative secondhook and peg shown on the right hand side of the figure in dashed lines;

FIG. 20 is a partial cross sectional view of an embodiment of aninterlocking wall design along line 21-21 of FIG. 19;

FIG. 21 is a partial cross sectional view of another embodiment of aninterlocking wall design along line 21-21 of FIG. 19;

FIG. 22A is a cross-sectional side view of an alternative embodiment ofan implant of the present invention with a pivoting trailing end that isalso a blocker in the trailing end opening position;

FIG. 22B is a cross-sectional side view of an alternative embodiment ofan implant of the present invention with a pivoting trailing end that isalso a blocker with the trailing end in the closed position; and

FIG. 23 is a trailing end perspective view of the implant of FIG. 22B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is intended to be representative only and notlimiting and many variations can be anticipated according to theseteachings, which are included within the scope of this inventiveteaching. Reference will now be made in detail to the preferredembodiments of this invention, examples of which are illustrated in theaccompanying drawings.

Shown in FIGS. 1-7 and 10-13, in accordance with the present invention,as embodied and broadly described herein, is one embodiment of anexpandable threaded artificial interbody spinal fusion implant 100 foranterior insertion across a disc space D between two adjacent vertebralbodies V of a human spine. Threaded implant 100 of the present inventionincludes an upper member 102 having an arcuate portion 104 adapted forplacement toward and at least in part within the upper of the adjacentvertebral bodies V and a lower member 106 having an arcuate portion 108adapted for placement toward and at least in part within the lower ofthe adjacent vertebral bodies V. Arcuate portions 104, 108 of upper andlower members 102, 106 have at least one opening 110, 112 incommunication with one another for permitting for the growth of bonefrom vertebral body V to adjacent vertebral body V through implant 100.Upper and lower members 102, 106 are articulated therebetween at anadjacent one of the proximal ends and the distal ends of upper and lowermembers 102, 106 and allow for rotation between the articulating membersat the end opposite the articulating end of implant 100. Upper and lowermembers 102, 106 have a first position relative to one another thatallows for a collapsed implant height and a second position relative toone another that allows for an increased height. Arcuate portions 104,108 of upper and lower members 102, 106 in the first position of thepresent invention are parallel to one another and form at least aportion of a cylinder along the length of implant 100. A portion 114,116 of at least one thread 118 is on an exterior 120 of each of opposedarcuate portions 104, 108 of upper and lower members 102, 106 forengaging adjacent vertebral bodies V.

While a specialized form of a blocker 121 is described in significantdetail below with reference to expander 122, blocker 121 need not be incontact with upper and lower members 102, 106 when implant 100 isinitially inserted into the implantation space. Blocker 121 may be ablock or any type of spacer that is inserted between the articulatedupper and lower members 102, 106 after implant 100 is positioned so asto hold portions of the upper and lower members 102, 106 spaced apartthe optimal height and angulation relative to one another. That is theimplant may be expanded with an extrinsic tool and then the expandedportions held apart in the second position by a third body blockerplaced therebetween. Further, a physician may be able to select from aseries of blockers having different heights usable with the sameimplant. The present invention includes expanding the implant with atool, such as a spreader or a distractor but is not limited to ascissors type, a rack and gear type, a threaded member type or any otherspecific type of movement mechanism. Each tool nevertheless preferablyengages upper and lower implant members 102, 106 to urge them apart.Blocker 121 is then inserted into contact with upper and lower members102, 106 to maintain implant 100 at an expanded height. The height ofthe gap created by expanding implant 100 may be measured so that theappropriately sized blocker 121 or specialized blocker, expander 122,may be inserted in implant 100 depending upon the amount of distractionof implant 100 desired by the surgeon.

Blocker 121 that is preferably in the form of expander 122 is locatedproximate at least one of the ends of the implant upper and lowermembers 102, 106 and holds at least a portion of upper and lower members102, 106 apart so as to maintain the increased height of implant 100 andresist the collapse of implant 100 to the collapsed implant height.Expander 122 in the present embodiment increases the implant height asmeasured in a plane passing through the mid-longitudinal axis of implant100 and upper and lower members 102, 106 during positioning of expander122 and as may be desirable is capable of selectively increasing theheight of the implant only.

Expander 122 in the present embodiment is adapted to rotate in a singledirection approximately 90 degrees to move from an initial (first)insertion position I, as best shown in FIGS. 1, 3 and 10, to a final(second) deployed or expanded position F, as best shown in FIG. 13, toincrease the maximum height H of implant 100. Expander 122 preferablyrotates in a plane perpendicular to the longitudinal axis L of implant100 to increase the maximum height H of implant 100. During rotation,expander 122 remains in the same perpendicular plane relative to thelongitudinal axis L of the implant. It is appreciated that an expanderwithin the scope of the present invention may be designed to: rotate ineither direction or both directions; rotate more than 40 degrees andless than 140 degrees; rotate more or less than 90 degrees; or rotate ina plane other than perpendicular.

Expander 122 has an opening 124 adapted to cooperatively engage a tool(not shown) used to rotate expander 122 to increase height H of implant100. Opening 124 is adapted to cooperatively engage a tool thatpreferably rotates about an axis parallel to the longitudinal axis L ofimplant 100 to rotate expander 122 to increase height H of implant 100.Opening 124 also may be used as a passageway to pass fusion-promotingsubstances through expander 122 and into implant 100. It is appreciatedthat the expander may also include a projection, a detent, or any otherconfiguration in place of or in addition to an opening so as tocooperatively engage a tool to move the expander.

In an alternative embodiment, an expander 122′ could have cutouts alongany portion of its perimeter not involved in the actual rotation asshown in FIG. 1A. In another alternative embodiment, a blocker 121having cutouts along a portion of its perimeter can be positioned intothe implant as shown in FIG. 1B. The cutouts can be used to engage araised area within the implant to lock blocker 121 or expander 122′ intoposition or be used by the surgeon to grasp blocker 121 with a tool thatcooperatively engages the cutouts to facilitate inserting blocker 121into the implant. Rather then having an opening, a projection, a detent,or a central aperture, a blocker 121′ alternatively could have two ormore recesses or holes placed on or through the proximal face to engagea tool as shown in FIG. 1C.

As shown in FIGS. 1, 6, 7, 10, 12A-12C, and 13, in one preferredembodiment of the present invention for anterior insertion, expander 122is located proximate the trailing end 126 of upper and lower members102, 106. While in a second embodiment as shown in FIGS. 14-16 forposterior insertion expander 222 is located proximate the leading end250. As shown if FIGS. 17-19, in third and fourth embodiments of thepresent invention for anterior insertion and possible use together,expanders 322 are located proximate each of leading and trailing ends330, 326 of implants 300.

Implant 100 preferably has an interior surface 128 and a hollow 130defined therein. Expander 122 of the present embodiment is locatedproximate interior surface 128 and more particularly proximate interiorsurface 128 at trailing end 126 of upper and lower members 102, 106. Asis preferred, hollow 130 between the ends is unobstructed by expander122 so as to allow for the unimpeded loading of the interior of theimplant with the desired fusion-promoting substances; thus, loading theimplant is easy. Further, this preferred configuration of implant 100makes available all of the volume of the hollow to containfusion-promoting substances and so as to permit for the growth of bonedirectly through the hollow unobstructed by the expander to adjacentvertebral bodies V. Unobstructed hollow 130 further allows for packingimplant 100 with fusion-promoting substances. It is appreciated thatdepending on the intended results, the expander also may be located atdistal end 126 or leading end 150 of upper and lower members 102, 106 oranywhere else within the implant. The unobstructed hollow preferably hasno mechanism extending along the longitudinal axis of the implant whenfinally deployed and the mechanism that moves the implant from a firstposition to a second position preferably does not move expander 122longitudinally through the hollow portion. The expander may work bypivoting on a surface in contact with an interior wall portion of atleast one of the upper and lower members 102, 106. Moreover, multipleexpanders may be used in contact with upper and lower members 102, 106at any location within the implant.

An alternative embodiment of an expander used with the present inventionincludes an expander having an external thread that cooperatives withconverging threaded portions of the upper and lower members 102, 106 toexpand the implant as the expander is rotated into position. Anotheralternative embodiment of an expander includes an expander having a camconfiguration to expand the implant upon rotation.

The mechanism or tool used to move the expander is not part of theimplant itself as the mechanism or tool is removed from the implant uponmoving the expander, e.g. such as to rotate it into place and thusexpand the implant to the final expanded position.

Expander 122 of the present embodiment moves arcuate portions 104, 108of upper and lower members 102, 106 from a parallel orientation P, asshown in FIGS. 1 and 11 where implant 100 has a generally circular crosssection in a first position at trailing end 126, to an angledorientation A, as shown in FIG. 12B where implant 100 has a generallyoblong cross section at trailing end 126, in a second position. Theimplant need not be a true cylinder as a cross section need not form acomplete circle having portions of the perimeter absent, less round,flattered, or other. It is appreciated that the expander also may movethe arcuate portions of the upper and lower members from a first heightat each end to a second and greater height at each end.

In this embodiment, each of upper and lower members 102, 106structurally cooperate with expander 122 so as to keep it located so asto function for its intended purpose. Each of upper and lower members102, 106 of the implant of FIG. 1 has a track 132, 134 within whichexpander 122 rotates. As best shown in FIGS. 1 and 13, track 132, 134 isconfigured to permit expander 122 to rotate therein and then to movefrom side to side within track 132, 134. Track 132 of upper member 102and track 134 of lower member 106 are in the same plane and the plane isperpendicular to the longitudinal axis of implant 100. It is appreciatedthat the track of the upper and lower members may be in differentplanes. Such a track design may be used with an expander with a step init or with offset tabs to engage tracks in different planes than oneanother. As with the expander, the tracks also may be at various anglesto the longitudinal axis of the implant including parallel with thelongitudinal axis of the implant. Other means for respectively engagingthe implants and the expander position thereof are anticipated andwithin the scope of the present invention.

In rotating the expander, the longer dimension of the expander issubstituted for the lesser dimension of the expander thuscorrespondingly increasing the maximum height of the implant from thefirst to the second position. As best shown in FIG. 9, the schematicrepresentation of a geometric configuration of a cross-section of anexpander 122 in accordance with one embodiment of the present invention,includes: a first dimension X corresponding to the height of expander122 when implant 100 is initially inserted into the spine and to thewidth of expander 122 when expander 122 is rotated to increase height Hof implant 100; and a second dimension Y corresponding to the width ofexpander 122 when implant 100 is initially inserted into the spine andto the height of expander 122 when expander 122 is rotated to increaseheight H of implant 100. Second dimension Y is greater than firstdimension X. Expander 122 has an upper surface 136, a lower surface 138,and side surfaces 140 as defined when expander 122 is positioned afterrotation to increase height H of implant 100. As used herein, the term“side surfaces” refers to those portions of expander 122 that extendfrom upper member 102 to lower members 106 after expander 122 has beenrotated into its final deployed, or second position to increase theheight H of implant 100. The “upper” and “lower” surfaces refer to thoseportions of expander 122 that are in contact with upper and lowermembers 102, 106 when implant 100 is in its second position andconfiguration and is fully expanded.

A preferred expander 122 is in the form of a modified rectangle orrhomboid. The expander generally has a longer dimension Y and a shorterdimension X. When the expander is inserted into a first position, theshort dimension X spans the distance between upper to the lower members102, 106 and when expander 122 is in the second position, the longerdimension Y of expander 122 spans the distance between upper and lowermembers 102, 106.

Expander 122 in one embodiment of the present embodiment has across-section with side surfaces 140 interesting upper and lowersurfaces 136, 138 at two junctions which may be diametrically opposedcorners 142 and two diametrically opposed arcs 144. Arcs 144 arepreferably each of the same radius and the modified hypotenuse MHbetween opposed arcs 144 generally approximates the distance betweenupper and lower surfaces 136, 138 such that, when expander 122 isrotated from an initial insertion position toward a final deployedposition, no substantial over-distraction occurs between adjacentvertebral bodies V. The modified hypotenuse MH of this embodiment of thepresent invention may be equal, slightly less than, or slightly greaterthan dimension Y of expander 122. Having the modified hypotenuse MH beslightly greater than the dimension Y offers the advantage of havingexpander 122 stabilized by an over-center position, such that moreenergy would be required to derotate the expander than for it to remainin the deployed or second position. By “without substantialover-distraction” what is meant is that the modified hypotenuse MHlength is closer to the expander dimension Y than to the unmodifiedhypotenuse UH; and is selected to allow the implant to preferablyoperate in the range of elastic deformation of the tissues about theoperated disc space. Corners 142 may form, but not necessarily, a90-degree angle and have an unmodified hypotenuse dimension UH.

By way of example, consider one embodiment of expandable implant 100 ofthe present invention having an optimum expanded height of 18 mm for agiven implantation space. Any implant bigger than 18 mm should not beused in this implantation space because during expansion of the implant,its height would move through the range of elastic deformation of thesurrounding tissues and after that the implant would crush the vertebralbone or tear ligaments. Inserting an expander such that when the implantis fully expanded allows the implant to be 18 mm would be ideal. It maybe that an implant having a 17.5 mm expanded height for thisimplantation space is nearly as good, but a 16 mm expanded height may betoo short to fit tightly within the implantation space. Using apreferred rectangular expander without any modification to thehypotenuse that is adapted to expand the implant to the optimum 18 mmfinal height would require the expander to have a hypotenuse causing theimplant to exceed the 18 mm expanded height temporarily during rotationof the expander. So turning the expander without a modified hypotenusewould break the vertebrae or tear the ligaments. In reverse, if onecould not expand the implant to more than 18 mm without causing damageto the spine, then an implant selected to have an expander having a fullunmodified hypotenuse so as to upon rotation temporarily cause theimplant height to be 18 mm would in the finally expanded position allowthe implant height to collapse such that there would be insufficientheight for the implant to adequately distract the implantation space.Generally, the modified hypotenuse of the expander is closer in lengthto dimension Y of the expander than to the unmodified hypotenuse.

As best shown in FIG. 1 in this particular embodiment, expander 122 hasa depth dimension Z that is less than that of first and seconddimensions Y, X. Expander 122 of the present embodiment has a fixedshape during movement from initial insertion position I to finaldeployed position F within implant 100.

As shown in FIGS. 22A, 22B, and 23, blocker 121 may also take the formof a trailing wall that articulates or hinges to the inside of implant100. The trailing wall may be left open during insertion of implant 100so as to trail behind the upper and lower members. The trailing walldoes not protrude outside of a projection rearward of the circumferenceof implant 100. Once implant 100 is implanted into position, thetrailing wall is rotated about one of its ends and pushed into positionand locked into place. This may occur by having the trailing wallcontact an inclined plane that leads up to a notch into which thetrailing wall locks into place. The trailing wall itself may also haveat least one opening in it to permit the further loading offusion-promoting materials into implant 100. Blocker 121 may also beadapted to cooperatively engage a tool used to move the blocker from aninitial position to a final position to increase the height of implant100, the tool being removable after moving blocker 121 into the finalposition.

Implant 100 may be configured to have a rotational articulation betweenthe upper and lower members adjacent one of the ends of the upper andlower members. The rotational articulation may be formed by the upperand lower members interdigitating so as to cooperatively engage. Therotational articulation may be configured so that engagement occurs whenthe upper and lower members are substantially perpendicular to oneanother. The rotational articulation may also be configured to remainengaged within a range of movement of the upper and lower membersresulting from positioning implant 100 between a first position of theupper and lower members relative to one another allowing for a collapsedimplant height and a second position relative to one another allowingfor an increased implant height.

At least one or both of the upper and lower members of implant 100 maybe configured to have a screw hole passing therethrough that is adaptedto receive a screw passing from an interior of implant 100 into anadjacent vertebral body. The screw may be adapted to pass from theinterior of implant 100 through the screw hole and into the adjacentvertebral body to anchor implant 100 to the adjacent vertebral body.

Implant 100 may be configured to have a side surface contoured tocooperate with another implant when implant 100 is in a final position.Implant 100 and the cooperating implant may have a combined widththerebetween less than the combined height of implant 100 and thecooperating implant.

While modified hypotenuse MH is illustrated as being between arcs 144 inthis preferred embodiment, the configuration of expander 122 to formmodified hypotenuse MH can take many forms, such that those junctionsare relieved so as to have the desired lesser dimension therebetween,including arcs, chamfers, a series of angled surfaces, or any othershape so long as the modified hypotenuse MH is sufficiently reduced indimension to function for the intended purpose according to the presentteaching.

An embodiment of the present invention where modified hypotenuse MH isslightly greater than height Y offers the advantage of an over-centereffect that locks expander 122 into place. In this instance, onceexpander 122 rotates past the diagonal of the modified hypotenuse MH,more force would be required to rotate it back from the final deployedposition to its insertion position than in an embodiment where modifiedhypotenuse MH is equal to or less than height Y. Preferably, expander122 offers a surgeon multiple sensory advantages including: the tactilefeel of expander 122 going over center and locking into place; thevisual of the handle of a tool rotating expander 122 such that the toolhandle goes from perpendicular to parallel, the reverse, or other, tothe disc space into place; and auditory from the sound of expander 122snapping into place.

Each of upper and lower surfaces 136, 138 of expander 122 of the presentembodiment lie generally in a plane and are generally parallel to oneanother. For any implant it is anticipated that a physician may be ableto select from a series of blockers or expanders allowing for varyingthe increase in the implant height. Side surfaces 140 and upper andlower surfaces 136, 138 are oriented so as to substantially form aparallelogram. Any of a number of configurations for the expander forincreasing the height of the implant is possible, based on the teachingsof the present application and such configurations as would be known toone of skill in the art are anticipated within the scope of the presentinvention.

The implant may preferably have an overlapping step-cut wall junctionbetween upper and power members 102, 106 which offers the advantage ofincreasing the lateral rigidity of implant 100 holding the implant inthe closed first position until expanded, and to the extent desiredretaining the fusion-promoting materials within. The wall junction maybe either solid or perforated. As best shown in FIG. 1, upper member 102in one embodiment of the preferred invention has interior walls 146extending from each side of arcuate portion 104 toward lower member 106.Interior wall 146 is aligned parallel to longitudinal axis L of implant100. Lower member 106 has an interior-contacting surface 148 adapted tocontact or receive interior wall 146.

In a preferred embodiment, upper and lower members 102, 106 arearticulated to one another so one of the respective ends of upper andlower members 102, 106 remain articulated while the other of therespective ends of upper and lower members 102, 106 are free to moveaway from one another. In a preferred embodiment the articulating meansis achieved without a third member such as an axle shaft passing throughthe implant. The articulating means preferably is formed into theimplant walls themselves in such a way that the two implant halves maybe articulated when the halves are at 90 degrees to each other and thenthe halves are moved toward each other for insertion into theimplantation space in the spine. The two halves are closed much like thecover of a book. The halves are locked together such thatdisarticulation will not occur when the implant is assembled for use.Any of a number of ways of articulating or joining upper and lowermembers 102, 106 is possible.

As best shown in FIG. 1 in this embodiment, upper and lower members 102,106 of the present embodiment have a pivot point between adjacent distalends 126 or leading ends 150 of upper and lower members 102, 106. Thepivot point in the present embodiment is at the end of implant 100opposite expander 122. The pivot point of the present embodimentoperates as a hinge or axle 152 but is formed out of the wallsthemselves so as to preferably not intrude into the implant interior orhollow or to block access thereto. Hinge 152 includes a projection 154extending radially from each side of arcuate portion 108 of lower member106 and a slotted bracket 156 extending from each side of arcuateportion 104 of upper member 102 for engaging projection 154. Brackets156 and projections 154 are configured such that engagement occurs whenupper and lower members 102, 106 are substantially perpendicular to oneanother. Brackets 156 and projections 154 are configured so as not todisengage within a range of movement of upper and lower members 102, 106that would occur when the implant is in use either during insertion orresulting from the expansion in height of implant 100.

As best shown in FIG. 11, interior wall 146 of upper member 102 of thepresent embodiment is unexposed when implant 100 is in initial insertionposition I. As shown in FIG. 12C, when implant 100 is in the expandedposition F, implant 100 has a shape such that each of arcuate portions104, 108 of upper and lower members 102, 106 are separated by at least aportion of interior wall 146, which in this position has an exposedside. The exposed side of the present embodiment is smooth and flat.

As best shown in FIG. 8, a cap 158 having an exterior surface 160 and aninterior surface 162 is used to close leading end 150 of implant 100.Interior surface 162 of cap 158 has spaced slots 164 about itscircumference to facilitate a snap fit between cap 158 and implant 100.Cap 158 and implant 100 can of course be adapted for either or both endsof implant 100.

As discussed above, implant 100 has a leading end 150 and a trailing end126. One of the ends preferably has a tool-engaging portion. Thistool-engaging portion is adapted to engage an insertion tool that holdsand rotates implant 100 into position. The tool-engaging configurationmay be an opening, and more particularly an opening that is along thelongitudinal axis of the implant to facilitate the use of an insertiontool that rotates implant 100 into an inserted position. Of course, thetool-engaging portion need not be an opening. A hole or a blind hole,threaded or otherwise, is preferred in another embodiment. In anotherpreferred embodiment the opening preferably is a threaded slot thatfunctions to cooperatively engage and disengage a tool for use ininserting implant 100. The opening either alone on the proximal end ofimplant 100 or in conjunction with other openings on the proximal endfunction to hold fusion-promoting material in implant 100 whilepermitting vascular access and bone growth through the opening oropenings.

Implants of the present invention may have an end adapted tocooperatively engage an implant driver. The anterior approach implantmay have a leading end, trailing end, or both ends that are adapted toengage a cap. One of the purposes for that cap includes restricting thepassage of fusion-promoting substances so that they remain loaded withinthe implant. Another purpose of the cap may be to add structural supportto the implant. The cap may be solid or it may have openingstherethrough. Any such openings could allow for the loaded material tostay within the implant while providing for vascular access to allow forthe ingrowth of blood vessels and the growth of bone through the end ofthe implant.

For a posterior approach implant the cap may be on either or both ends.The trailing end of the implant in a posterior approach implant hasdirect exposure to the spinal canal where the spinal cord and nerveroots are located. A cap on a posterior approach implant may be for thepurpose of sealing off the spinal canal from the fusion-promotingsubstances contained in the hollow interior of the implant so that nobone grows into the canal. Further, the present invention implant may beused in combination with chemical substances and/or compounds applied atthe trailing end of the implant to inhibit scar formation, and the capmay be of benefit in shielding the fusion-promoting substances containedin the implant from these scar formation inhibiting chemicals andcompounds. It may also be for the purposes identified herein used inassociation with the leading end cap of an anterior approach implant.

Shown in FIGS. 14-16, in accordance with the present invention, asembodied and broadly described herein, is a second embodiment of anexpandable threaded artificial interbody spinal fusion implant 200 forposterior insertion across a disc space D between two adjacent vertebralbodies V of a human spine. Threaded implant 200 of the present inventionincludes an upper member 202 having an arcuate portion 204 adapted forplacement toward and at least in part within the upper of the adjacentvertebral bodies V and a lower member 206 having an arcuate portion 208adapted for placement toward and at least in part within the lower ofthe adjacent vertebral bodies V. Implant 200 in FIGS. 14 and 15 is shownbeing implanted into the spine from the posterior aspect with expander222 on the distal end 226 or leading end 250 of implant 200. Whileanterior and posterior aspect approaches have been illustrated herein,the present invention is not limited to these illustrated approaches. Inparticular, but not limited thereto, the threaded implant of the presentinvention also may be used in threaded implants for insertion from thetranslateral aspect of the spine as disclosed by Michelson in U.S. Pat.No. 5,860,973, which is incorporated herein by reference.

As best shown in FIG. 16, tracks 232, 234 of upper and lower members202, 206 of the second embodiment have a cooperating surface 266 andexpander 222 has a corresponding cooperating surface 268 that contactscooperating surface 266 of tracks 232, 234 to orient expander 222 in apredetermined location. The cooperating surfaces orient expander 222within implant 200 such that the axis of rotation of expander 222 isparallel to the longitudinal axis of implant 200 and more particularlycenter expander 222 within implant 200 such that the axis of rotation ofexpander 222 coincides with longitudinal axis L of implant 200.

Tracks 232, 234 include sides 270 having cooperating surface 266 andexpander 222 has corresponding cooperating surface 268 used to orientexpander 122 in a predetermined location. Cooperating surface 266 ofside 270 is a detent and corresponding cooperating surface 268 ofexpander 222 is a projection. The projection preferably projects awayfrom expander 222 in a direction parallel to the longitudinal axis ofimplant 200. The detent and the projection preferably center expander222 within implant 200 such that the axis of rotation of expander 222coincides with the longitudinal axis of implant 200.

Shown in FIGS. 17-19, in accordance with the present invention, asembodied and broadly described herein, is a third embodiment of anexpandable threaded artificial interbody spinal fusion implant 300 forinsertion across a disc space D between two adjacent vertebral bodies Vof a human spine. Threaded implant 300 of the present invention includesan upper member 302 having an arcuate portion 304 for orientation towardthe upper of adjacent vertebral bodies V and a lower member 306 havingan arcuate portion 308 for orientation toward the lower of the adjacentvertebral bodies V.

Implant 300 of the present embodiment may include any of the variousfeatures disclosed in association with implant 100 and implant 200disclosed herein. Implant 300 further includes a side surface 372contoured to cooperatively receive another implant. See U.S. Pat. No.5,593,409 by Michelson for a discussion of the advantages associatedwith placing implants in side-in-side contact.

Another aspect of implant 300 is that its upper and lower members 302,306 have screw holes 374 passing therethrough adapted to receive a screw378 passing from the interior of implant 300 into adjacent vertebralbodies V to anchor implant 300 to an adjacent vertebral body V.

The articulation may be of one of two general types, examples of whichare each herein disclosed. As shown in previously described embodimentsof the present invention, the articulation may allow rotation about thearticulation. A second type of articulation allows for both rotation andexpansion at the point of articulation. An example of this is shown inFIG. 19, where a peg and hook design is utilized. While in this exampleboth functions, that is rotation or pivoting, and captured or limitedexpansion with a fixed end point or stop, occur at the same location.Alternatively, and without departing from the teachings of the presentinvention, those functions can be divided. By way of example only, andnot limitation, expansion can be allowed and controlled by aninterlocking wall design, as shown by the interlocking members in thealternative embodiments of FIGS. 20 and 21. Various other structuralfeatures as would be obvious to one of ordinary skill in the art afterthe teachings herein can similarly be employed.

A fixed end point for the implant expansion is preferred for the properfunctioning of the opposed bone screws. A purpose of the opposed bonescrews is to rigidly secure the implant within the vertebral segment. Afurther purpose is to pull each of the adjacent vertebral bodies towardthe implant and towards each other so as to have a construct resistantto the deleterious effects of vertebral rocking as may otherwise occurwith spinal flexion and extension absent such restraint. If thearticulation device captured the upper and lower members together, as inthe embodiments of FIGS. 1-16, by closely encircling a post then theimplant could not expand at that location. So the coupling mechanism ofFIG. 19 permits the upper and lower members to remain articulated,permits the implant to expand, and permits the screws to pull againstthe implant and each other, in opposite directions and to pull the bonestoward each other. The optional extended slot and peg configuration onthe right-hand side of FIG. 19 illustrated in dashed image lines is notneeded to hold the implant together.

In accordance with this embodiment of the present invention, a secondexpander may be located at least in part between the upper and lowermembers for moving at least a portion of the upper and lower membersaway from one another to increase the height of the implant defined bythe maximum distance between the arcuate portions of the upper and lowermembers. All of the features described herein for the expander may alsobe applicable to the second expander. Additionally, the second expandermay be located proximate an end of the implant opposite the otherexpander, thereby providing an implant capable of being expanded at bothends of implant. The increased height of the implant resulting frommoving the two expanders may be the constant or varied along the lengthof the implant according to the desired configuration of the implant.

The expandable threaded spinal fusion implant may be made of artificialor naturally occurring materials suitable for implantation in the humanspine. The implant can comprise bone including, but not limited to,cortical bone. The implant can also be formed of material other thanbone, such as metal including, but not limited to, titanium and itsalloys or ASTM material, surgical grade plastics, plastic composites,ceramics, or other materials suitable for use as a threaded spinalfusion implant. The plastics may be bioresorbable. The threaded spinalfusion implant of the present invention can further be formed of bonegrowth promoting materials, including but not limited to, bonemorphogenetic proteins, hydroxyapatite, and genes coding for theproduction of bone. The threaded implant can be treated with a bonegrowth promoting substance, can be a source of osteogenesis, or can beat least in part bioabsorbable. The threaded implant of the presentinvention can be formed of a porous material.

The expandable threaded spinal fusion implant of the present inventionmay be coated with, comprised of, be used in combination with, or have ahollow for containing bone growth promoting materials, including but notlimited to, bone morphogenetic proteins, hydroxyapatite, and genescoding for the production of bone. The threaded spinal fusion implant ofthe present invention can be formed of a material that intrinsicallyparticipates in the growth of bone from one of adjacent vertebral bodiesV to the other of adjacent vertebral bodies V.

While various embodiments of the present invention are presented by wayof example only and not limitation, common to each of them, is that theexpandable threaded spinal fusion implant for insertion across discspace D between two adjacent vertebral bodies V of a human spine has anupper member having an arcuate portion adapted for placement toward andat least in part within the upper of the adjacent vertebral bodies V.The implant also has a lower member having an arcuate portion adaptedfor placement toward and at least in part within the lower of theadjacent vertebral bodies V. The arcuate portions of the upper and lowermembers have at least one opening. The openings of the upper and lowermembers are in communication with one another to permit for the growthof bone from vertebral body V to adjacent vertebral body V through theimplant. At least a portion of a thread for engaging adjacent vertebralbodies V is on the exterior of each of the opposed arcuate portions ofthe upper and lower members. A blocker in the form of an expanderpreferably is located proximate at least one of the ends to hold atleast a portion of the upper and lower members apart from one another toincrease the implant height.

There is disclosed in the above description and the drawings implants,which fully and effectively accomplish the objectives of this invention.However, it will be apparent that variations and modifications of thedisclosed embodiments may be made without departing from the principlesof the invention or the scope of the appended claims.

1. An apparatus comprising: an expandable implant for use in the humanbody, said implant having a leading end, a trailing end, amid-longitudinal axis through said leading and trailing ends, moveableportions, and an interior; and an expander for moving apart saidmoveable portions of said implant, said expander including: an uppersurface, a lower surface, and side surfaces, said side surfacesintersecting said upper and said lower surfaces at a pair ofdiametrically opposed corners and a pair of diametrically opposed arcs;a first distance between said upper and lower surfaces, a seconddistance between said side surfaces, and a third distance between saidopposed arcs, the first distance being greater than the second distance;and an axis of rotation about which said expander is rotatable so thatsaid expander moves apart the moveable portions of said implant whensaid opposed arcs are rotated against the moveable portions of saidimplant, the axis being perpendicular to said first and seconddistances.
 2. The apparatus of claim 1, wherein said third distancegenerally approximates said first distance.
 3. The apparatus of claim 1,wherein said third distance is greater than said first distance.
 4. Theapparatus of claim 1, wherein said third distance is less than saidfirst distance.
 5. The apparatus of claim 1, further comprising a fourthdistance between said opposed corners, said fourth distance beinggreater than said third distance.
 6. The apparatus of claim 1, furthercomprising a depth parallel to the axis of rotation of said expander,said depth being less than said first distance.
 7. The apparatus ofclaim 1, further comprising a depth parallel to the axis of rotation ofsaid expander, said depth being less than said second distance.
 8. Theapparatus of claim 1, wherein said expander has an outer perimeteradapted to contact a portion of said implant, said outer perimeter beingnon-threaded.
 9. The apparatus of claim 1, wherein each of said upperand lower surfaces lie generally in a plane.
 10. The apparatus of claim1, wherein said upper and lower surfaces are generally parallel to oneanother.
 11. The apparatus of claim 1, wherein said side surfaces andsaid upper and lower surfaces are oriented to substantially form aparallelogram.
 12. The apparatus of claim 1, wherein said twodiametrically opposed arcs are each of the same radius.
 13. Theapparatus of claim 1, wherein said two diametrically opposed arcs arearcs of the same circle.
 14. The apparatus of claim 1, wherein said twodiametrically opposed corners each form a 90-degree angle.
 15. Theapparatus of claim 1, wherein said expander has a fixed shape duringmovement from an initial insertion position to a final deployed positionwithin said implant.
 16. The apparatus of claim 1, wherein said expanderincludes an opening adapted to cooperatively engage a tool used to movesaid expander from an initial position to a final position to increasethe height of said implant.
 17. The apparatus of claim 16, wherein saidopening is non-threaded.
 18. The apparatus of claim 16, wherein saidopening is coaxial with the axis of rotation.
 19. The apparatus of claim16, wherein said opening is offset from the axis of rotation.
 20. Theapparatus of claim 1, wherein said expander has an outer perimeter, theouter perimeter including at least one removed portion for engaging atool used to move said expander from an initial position to a finalposition to increase the height of said implant.
 21. The apparatus ofclaim 20, wherein said removed portion is concavedly-shaped.
 22. Theapparatus of claim 1, wherein at least two of said moveable portionsinclude at least one opening in communication with said interior of saidimplant to permit bone growth through said implant.
 23. The apparatus ofclaim 1, wherein said implant has a depth between said leading andtrailing ends, said expander having a depth dimension that is less thanhalf the depth of said implant.
 24. The apparatus of claim 1, whereinsaid implant has a width perpendicular to the mid-longitudinal axis ofsaid implant, said second distance being approximately one-half thewidth of said implant.
 25. The apparatus of claim 1, wherein saidexpander is adapted to rotate in a plane perpendicular to themid-longitudinal axis of said implant.
 26. The apparatus of claim 1,wherein said expander is adapted to remain in a fixed location along themid-longitudinal axis while transitioning said implant from anunexpanded position to an expanded position.
 27. The apparatus of claim1, wherein said implant comprises: an upper member having a portionbeing at least in part arcuate adapted for contact with an adjacent boneportion; and a lower member having a portion being at least in partarcuate adapted for contact with an adjacent bone portion, at least aportion of said upper and lower members being moveable relative to oneanother.
 28. The apparatus of claim 27, wherein said expander is adaptedto slide along at least a portion of at least one of said upper andlower members.
 29. The apparatus of claim 27, wherein said arcuateportions of said upper and lower members are arcs of the same circle.30. The apparatus of claim 27, wherein said upper and lower members eachhave a length, the entire length of said upper and lower members beingmovable relative to the mid-longitudinal axis.
 31. The apparatus ofclaim 1, wherein said implant is adapted for insertion at least in partbetween two adjacent vertebral bodies of the spine.
 32. The apparatus ofclaim 31, wherein said implant comprises: an upper member having aportion being at least in part arcuate adapted for placement toward andat least in part within one of the adjacent vertebral bodies; and alower member having a portion being at least in part arcuate adapted forplacement toward and at least in part within the other of the adjacentvertebral bodies, at least a portion of said upper and lower membersbeing moveable relative to one another.